Solid liquid interfaces

In this chapter we discuss preparative routes for inorganic materials in three basic types of systems involving the presence of a distinct solid-liquid interface those in which the liquid and solid phases are of the same chemical identity (solidification and vitrification processes), those in which the liquid and solid phases are not of the same chemical identity (crystallization, precipitation), and the special case in which the liquid phase is a pure ionic liquid or molten salt. Ionic liquids can serve as the solvent as well as a templating agent, and the liquid components may or may not become incorporated into the final solid product. We also discuss two areas where the distinct solid-liquid interface becomes somewhat blurred namely, sol-gel and solvothermal processes. 

Inorganic Materials Synthesis and Fabrication, By John N. Lalena, David. A. Cleary, Everett E. Carpenter, and Nancy F. Dean Copyright 2008 John Wiley Sons, Inc. 

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The statistical mechanical approach, density functional theory, allows description of the solid-liquid interface based on knowledge of the liquid properties [60, 61], This approach has been applied to the solid-liquid interface for hard spheres where experimental data on colloidal suspensions and theory [62] both indicate 0.6 this... 

In recent years, advances in experimental capabilities have fueled a great deal of activity in the study of the electrified solid-liquid interface. This has been the subject of a recent workshop and review article [145] discussing structural characterization, interfacial dynamics and electrode materials. The field of surface chemistry has also received significant attention due to many surface-sensitive means to interrogate the molecular processes occurring at the electrode surface. Reviews by Hubbard [146, 147] and others [148] detail the progress. In this and the following section, we present only a brief summary of selected aspects of this field. 

Molecular dynamics and density functional theory studies (see Section IX-2) of the Lennard-Jones 6-12 system determine the interfacial tension for the solid-liquid and solid-vapor interfaces [47-49]. The dimensionless interfacial tension ya /kT, where a is the Lennard-Jones molecular size, increases from about 0.83 for the solid-liquid interface to 2.38 for the solid-vapor at the triple point [49], reflecting the large energy associated with a solid-vapor interface. 

A more recent model for the preexponential factor including viscous flow across the solid-liquid interface is [14]... 

The importance of the solid-liquid interface in a host of applications has led to extensive study over the past 50 years. Certainly, the study of the solid-liquid interface is no easier than that of the solid-gas interface, and all the complexities noted in Section VIM are present. The surface structural and spectroscopic techniques presented in Chapter VIII are not generally applicable to liquids (note, however. Ref. 1). There is, perforce, some retreat to phenomenology, empirical rules, and semiempirical models. The central importance of the Young equation is evident even in its modification to treat surface heterogeneity or roughness. ... 

This section represents a continuation of Section VII-5, which dealt primarily with the direct estimation of surface quantities at a solid-gas interface. Although in principle some of the methods described there could be applied at a solid-liquid interface, very little has been done apart from the study of the following Kelvin effect and nucleation studies, discussed in Chapter IX. 

The Solid-Liquid Interface—Adsorption from Solution... 

Of particular interest has been the study of the polymer configurations at the solid-liquid interface. Beginning with lattice theories, early models of polymer adsorption captured most of the features of adsorption such as the loop, train, and tail structures and the influence of the surface interaction parameter (see Refs. 57, 58, 62 for reviews of older theories). These lattice models have been expanded on in recent years using modem computational methods [63,64] and have allowed the calculation of equilibrium partitioning between a poly-... 

Proteins often have the same high-affinity isotherms as do synthetic polymers and are also slow to equilibrate, due to many contacts with the surface. Proteins, however, have the additional complication that they can partially or completely unfold at the solid-liquid interface to expose their hydrophobic core units to a hydrophobic surface... 

G. J. Fleer and J. Lyklema, Adsorption from Solution at the Solid/Liquid Interface, Academic Press, Orlando, FL, 1983, Chapter 4, pp. 153-220. 

Corrosion protection of metals can take many fonns, one of which is passivation. As mentioned above, passivation is the fonnation of a thin protective film (most commonly oxide or hydrated oxide) on a metallic surface. Certain metals that are prone to passivation will fonn a thin oxide film that displaces the electrode potential of the metal by +0.5-2.0 V. The film severely hinders the difflision rate of metal ions from the electrode to tire solid-gas or solid-liquid interface, thus providing corrosion resistance. This decreased corrosion rate is best illustrated by anodic polarization curves, which are constructed by measuring the net current from an electrode into solution (the corrosion current) under an applied voltage. For passivable metals, the current will increase steadily with increasing voltage in the so-called active region until the passivating film fonns, at which point the current will rapidly decrease. This behaviour is characteristic of metals that are susceptible to passivation. 

Surface science studies of corrosion phenomena are excellent examples of in situ characterization of surface reactions. In particular, the investigation of corrosion reactions with STM is promising because not only can it be used to study solid-gas interfaces, but also solid-liquid interfaces. 

Bain C D 1995 Sum-frequency vibrational spectroscopy of the solid-liquid interface J. Chem. See. Faraday Trans. 91 1281-96... 

One of the most important advances in electrochemistry in the last decade was tlie application of STM and AFM to structural problems at the electrified solid/liquid interface [108. 109]. Sonnenfield and Hansma [110] were the first to use STM to study a surface innnersed in a liquid, thus extending STM beyond the gas/solid interfaces without a significant loss in resolution. In situ local-probe investigations at solid/liquid interfaces can be perfomied under electrochemical conditions if both phases are electronic and ionic conducting and this... 

Barker A L, Gonsalves M, Maepherson J V, Slevin C J and Unwin P R 1999 Scanning electrochemical microscopy beyond the solid/liquid interface Anal. Chim. Acta 385 223... 

Manne S 1997 Visualizing self-assembly Force microscopy of ionic surfactant aggregates at solid-liquid interfaces Prog. Colloid Polym. Sol. 103 226-33... 

Manne S and Gaub FI E 1995 Molecular organization of surfactants at solid-liquid interfaces Science 270 1480-3... 

Partyka S, Linsheimer M and Faucompre B 1993 Aggregate formation at the solid-liquid interface the calorimetric evidence Colloids Surf. A 76 267-81... 

Cavitation damage is a fonn of deterioration associated with materials in rapidly moving liquid environments, due to collapse of cavities (or vapour bubbles) in the liquid at a solid-liquid interface, in the high-pressure regions of high flow. If the liquid in movement is corrosive towards the metal, the damage of the metal may be greatly increased (cavitation corrosion). 

The equivalent equations for heterogeneous and quasi-heterogeneous systems (tire latter are small vesicles which can practically be handled as homogeneous systems, but which are nevertlieless large enough to possess a macroscopic solid-liquid interface) are dealt witli in section C2.14.7. 

Current emphasis is on the behaviour of proteins at tire solid-liquid interface, but liquid-air and liquid-liquid interfaces, which were actually investigated much earlier [131], are still important. 

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